The measurement of humidity variations in gases resulting from the adsorption of water on to surfaces

Adsorption of water vapour on to solid surfaces can cause measurement anomalies in a number of applications. In the particular case of interference gas refractometry this produces a reduction in the humidity of the moist gas contained within the sample cell, leading to errors in the measurement of the refractive index. A technique is described for investigating these anomalies for a variety of material surfaces, and results from fused silica and stainless steel are discussed.